1. Field of the Invention
The invention relates to the field of the prevention of lavatory fluid leakage in connection with aircraft in flight where blue ice forms on aircraft surfaces.
2. Description of Prior Art
Aircraft that contain in-flight lavatory systems usually experience what is known as a "blue icing" condition. When the aircraft is in flight, air inside the aircraft is pressurized. At high altitudes, the outside air pressure is much lower and the air temperature is much colder than the inside air pressure and temperature of the aircraft causing a pressure differential and a temperature gradient. Any water that is disposed on the aircraft skin, whether if be from atmospheric accumulation or from leakage from inside the aircraft immediately freezes and accumulates in a mass on the aircraft skin.
Aircraft with lavatories contain a lavatory fluid reservoir which serves as the depository for all lavatory fluid and waste going to and from the lavatory or lavatories of the aircraft. A disposal hose connects from the lavatory fluid reservoir to a service valve located near the service door of the aircraft. When the aircraft has landed, the lavatory fluid and waste in the lavatory fluid reservoir can be removed from the reservoir by a suction hose of a service truck which is connected by ground crews to the service valve. In flight, the service valve along with the service door are shut and sealed.
Despite the service valve and service door being shut during flight, and despite the attempt to provide leak-proof seals, the differential in air pressure once the aircraft is in flight causes lavatory fluid to leak out of the service valve and pool around the inside base of the service door. The constant expansion and contraction of the aircraft and all of its parts with each take off and landing cycle due both to temperature and pressure cycling makes the retention of a leak-proof seal at the service valve and door impossible. The repeated rough handling of the service valve and door and their seals by repeated access by the ground crew also contributes to the comprise of the seal integrity. Sooner or later the occurrence of a leak of the lavatory fluid through the seal of the service valve and door will occur.
The fluid then leaks through the service valve and eventually through the service door. After leaking through the seal on the service door to the outer surface of the aircraft near the lower edge of the service door, a blue ice chunk or frozen solid mass of lavatory fluid results because of the cold outside air temperatures. The name "blue icing" comes from the fact that the frozen lavatory fluid has an additive for odor and sanitation, which is usually blue in color.
Blue ice has fallen from aircraft to the ground and unto homes, causing severe damage to structures and automobiles which have been hit and putting persons at jeopardy to injury. Even more often, depending in part on the proximity of the service door to the engine intakes, blue ice can and has entered jet engines resulting in engine failures and in some cases the destruction and physical detachment of the entire engine from the aircraft, not only jeopardizing land-based property and life, but also airborne property and life.
Therefore, what is needed is an apparatus and a method by which lavatory fluid can be prevented from leaking through the service door and, eventually, becoming blue ice.